The present invention relates generally to mixer valves for internal combustion engines, and more particularly to gas/air mixer assemblies for internal combustion engines that utilize gaseous fuel supplies.
As is well understood in the art, internal combustion engines operate to convert the potential energy of a fuel source into useful power to perform a work function. Specifically, internal combustion engines operate by combusting a fuel to drive a piston to create motion to drive a load. To increase the efficiency of the combustion, internal combustion engines mix a quantity of fuel with air to enhance the combustibility thereof. Fuel metering valves are used to meter a proper amount of fuel into the combustion chamber. The control of the fuel metering valve may take into account various parameters including throttle position, the temperature and operating mode of the engine, the sensed emissions, etc. If the fuel/air mixture is too rich, i.e. contains too much fuel, the combustion in the chamber will not be complete, resulting in increased emissions. If the fuel/air mixture is too lean, i.e. not enough fuel for the volume of air, the engine performance will be decreased possibly resulting in stalling or damage to the engine.
While various mechanisms and complicated algorithms exist to control the proper metering of an amount of fuel to be combusted, little attention has been paid to the actual mixing of the metered fuel and air prior to combustion. Indeed, even in supercharged and turbocharged engine applications wherein the air supplied to the mixing chamber is pressurized, the actual mixing of the fuel and air is not typically controlled. That is, the metered amount of fuel and the air to be mixed are brought together in a manner that does not specifically control the proper mixing of these two inputs. As a result, the actual mixture of fuel and air may differ somewhat for each combustion cycle. As a result, the emissions from such an engine, and indeed its performance, may well vary. While such a situation occurs in internal combustion engines that utilize liquid fuels, the problem is particularly acute in internal combustion engines that utilize gaseous fuel, e.g. propane.
The reason this problem is of particular concern for gaseous fuel engines, besides the obvious decreased efficiency, increased cost, and increased environmental impact, is because such engines are typically used in closed environments such as factories. One such application used commonly in factories is the forklift. Since forklifts are used extensively in factories as well as in storage warehouses, home improvement stores, indoor lumberyards, etc., which may not have the best ventilation, any unnecessary increase in emissions is unacceptable.
In a typical gaseous fuel burning internal combustion engine, the gaseous fuel is supplied from a sealed tank through a gas regulator to a gaseous fuel metering valve. The gaseous fuel metering valve typically supplies an amount of the gaseous fuel to an engine manifold wherein it is mixed with a supply of air to form the combustible air fuel mixture that will be combusted in the internal combustion engine. While one might think that the mixture of a gaseous fuel such as propane and air would be a relatively simple matter resulting in a very homogenous air fuel mixture, the fact is that it is very difficult to achieve a homogenous air fuel mixture in the mixing chamber of the internal combustion engine prior to combustion. As a result, throttle response is affected and may be nonlinear or inconsistent. Further, and of great concern when used in enclosed spaces, the inconsistent nature of the gaseous fuel and air mixture results in inconsistent combustion and increased emissions.
Therefore, there exists a need in the art for a gas/air mixing device that will provide proper mixing of the gaseous fuel and air without adversely affecting throttle response, and which will alleviate the problem of increased emissions due to poor gaseous fuel/air mixture prior to combustion.
In view of the above, it is an objective of the present invention to provide a new and improved gas/air mixing device that overcomes the above-described and other problems existing in the art. More particularly, it is an objective of the present invention to provide a new and useful gas/air mixing device having particular application to internal combustion engines that utilize gaseous fuel. Further, the gas/air mixing device of the present invention will preferably provide such increased benefits without moving parts in a particular application. Further, the mixing device of the present application may be easily adapted to different applications providing increased or decreased flow as required thereby.
In one embodiment of the present invention, the mixing device provides improved gas/air mixture without reducing throttle response by minimizing air turbulence at the point of gaseous fuel air mixing. Preferably, the mixing device of the present invention provides a Venturi-type mixing body configured to provide maximum velocity airflow in a direction perpendicular to the introduction of the gaseous fuel.
In one embodiment of the present invention, the mixing device includes a flow tube positionable in relation to a restriction body. The flow tube preferably includes a radiused semi-circular lip around which air may flow without substantial increased turbulence. Further, the flow tube preferably includes an upper flat forming, in relation to the mixing chamber body, a substantially laminar flow corridor through which the incoming air is drawn by the Venturi formed between the restriction body and the outward flared flow tube. The gaseous fuel discharge port is preferably located to provide gaseous fuel flow in a direction perpendicular to the substantially laminar airflow through this corridor. Preferably, the volume of air flow entering this chamber is controlled by a relative position between the flow tube and the restriction body, each of which have a profiled surface that vary the cross-sectional area as the two members are varied in relation to one another. However, once a particular engine application is selected, these two members are fixed in relation to one another such that proper mixing of the fuel and air may be maintained.